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remove lagging from cold water tank in summer ?

I have 2 large plastic water tanks in my loft (= a small header for
the CH). The tanks are black plastic and interconnected. They are also
well lagged.

I was thinking about solar Hot water and it occurred to me that during
the summer it may be of benefit to remove the insulation from the
tanks. The attic can get unbearably hot and presumably the insulation
is working against any preheating of the water before it hits the
boiler for HW ? I'd guess by pure infra red radiation the plastci tank
would heat fractionally on hot days ?

Of course with the mad UK weather there is always the risk of a cold
spell, but I'd guess for a few months the risk would be low.

Hi,
I have 2 large plastic water tanks in my loft (= a small header for
the CH). The tanks are black plastic and interconnected. They are also
well lagged.
I was thinking about solar Hot water and it occurred to me that during
the summer it may be of benefit to remove the insulation from the
tanks. The attic can get unbearably hot and presumably the insulation
is working against any preheating of the water before it hits the
boiler for HW ? I'd guess by pure infra red radiation the plastci tank
would heat fractionally on hot days ?
Of course with the mad UK weather there is always the risk of a cold
spell, but I'd guess for a few months the risk would be low.
anyone do this and get any benefit

Don't! It will stagnate at an elevated temperature, and be liable to spread
legionella, particulary if there is a cold draw off from it. It must be kept
at below 20degC.

--
B Thumbs
Change lycos to yahoo to reply

Many thanks. I had not thought of that. So how do solar water heating
systems avoid this ? I'd assumed they preheat stored water before it
enters the boiler.

Last year while on holiday in Crete I noticed lots of houses
*appeared* to have black plastic water tanks on their flat roofs. I'd
assumed this was a cheap way to get some raise of temperature.

Hi,
I have 2 large plastic water tanks in my loft (= a small header for
the CH). The tanks are black plastic and interconnected. They are also
well lagged.
I was thinking about solar Hot water and it occurred to me that during
the summer it may be of benefit to remove the insulation from the
tanks. The attic can get unbearably hot and presumably the insulation
is working against any preheating of the water before it hits the
boiler for HW ? I'd guess by pure infra red radiation the plastci tank
would heat fractionally on hot days ?
Of course with the mad UK weather there is always the risk of a cold
spell, but I'd guess for a few months the risk would be low.
anyone do this and get any benefit

Don't! It will stagnate at an elevated temperature, and be liable to spread
legionella, particulary if there is a cold draw off from it. It must be kept
at below 20degC.

--
B Thumbs
Change lycos to yahoo to reply

Many thanks. I had not thought of that. So how do solar water heating
systems avoid this ? I'd assumed they preheat stored water before it
enters the boiler.

Last year while on holiday in Crete I noticed lots of houses
*appeared* to have black plastic water tanks on their flat roofs. I'd
assumed this was a cheap way to get some raise of temperature.

I dont think you can have a solar heater with a combi if thats what
you mean, you need a stored hot water cylinder system which heats the
water to over 60 degrees C.

On 29 Mar 2007 13:19:38 -0700 someone who may be "jives11"
wrote this:-
Many thanks. I had not thought of that. So how do solar water heating
systems avoid this ? I'd assumed they preheat stored water before it
enters the boiler.

Assuming you are thinking of the domestic hot water heating part of
a combination boiler, the solar panel will feed a relatively small
hot water cylinder from which water to the boiler is drawn (either
directly or via a heat exchanger). The combination boiler must be
able to accept heated water.

On 30 Mar, 06:39, David Hansen
wrote:
On 29 Mar 2007 13:19:38 -0700 someone who may be "jives11"
wrote this:-
Many thanks. I had not thought of that. So how do solar water heating
systems avoid this ? I'd assumed they preheat stored water before it
enters the boiler.

Assuming you are thinking of the domestic hot water heating part of
a combination boiler, the solar panel will feed a relatively small
hot water cylinder from which water to the boiler is drawn (either
directly or via a heat exchanger). The combination boiler must be
able to accept heated water.

Thanks. I wasn't thinking of a combi. My system is a fully pumped
system with ho****er tank.

I had assumed that anything that raised the temperature of the water
in the HW header tank would reduce the amount of gas and hence CO2
consumed.

So how do solar hot waters heat the water ? Is there a secondary coil
in the hot water tank, through which the solar heated water is pumped
OR do they raise the temperature of the water in the storage tank.
Sounds like the latter is unlikely given the health issues with having
quantities of warm water hanging around with only a lid protecting it.

On 30 Mar 2007 02:16:52 -0700 Jives11 wrote :
So how do solar hot waters heat the water ? Is there a secondary coil
in the hot water tank, through which the solar heated water is pumped

This is the preferred method, though you can put s pre-heat cylinder in
the existing cylinder feed
OR do they raise the temperature of the water in the storage tank.

No, partly for the reason you give (legionnaires), also because there
is potential for this water to become dangerously hot and it is being
fed to uncontrolled places (e.g. basin 'cold' taps), also a plastic
cistern full of very hot water is not a good idea.